Disposable filter units are commonly products of industrial mass manufacturing and are used in chemical, physical and pharmaceutical laboratories for the pressure filtration of liquids and gases.
The filter unit includes a filter element which is normally a filter diaphragm fixed (e.g. by welding) between two housing parts of a filter housing. The filter element is supported across its whole surface by filter support means which are formed inside the housing parts as a part of the housing.
A filter unit of this kind is known, for example, from German patent application DE 32 02 330.8 A1. The filter support means used in this filter unit comprises on its side facing the flat filter element a plain surface interrupted by a plurality of concentrically arranged circular channels, intersected by a group of radially extending channels partially extending into a respective connecting sleeve. The inner cross-section of the radially extending channels increases from the peripheral area of the filter housing to the centrally arranged connecting sleeve. However, though establishing good and uniformly distributed support characteristics across the whole surface of the filter element, the fluid flow through such a filter is throttled significantly inspite of the increasing cross-section of the radially extending channels. Filters of this kind can be used only for relatively low flow rates.
In contrast, significantly higher flow rates, with respect to the area of the filter element, can be achieved in a disposable filter unit known from U.S. Pat. No. 3,782,083. This filter unit is used only for the filtration of gases and the connecting sleeves therein expand continuously like a funnel forming a hyperbolic inner surface of the housing. Axial webs are formed at these inner surfaces and are radially star-type distributed, the radial edges of which webs are in the same plane supporting the filter element. However, a disadvantage of this filter unit is that it can be loaded only with low pressures in order not to damage the filter element by tearing.